I think this exists in the standard Dev Tools / inspector.
Edit a CSS file in the Sources tab of the Dev Tools then right click and click Local Modifications. Also right click on the file (in the whitespace) and click Save. Then click History and you can see the exact changes that you made and even revert.
I've never used it though, not sure how useful it is.
There is also a Workspace feature in the Dev Tools options which might have something closer to what you are looking for.
Edit a CSS file in the Sources tab of the Dev Tools then right click and click Local Modifications. Also right click on the file (in the whitespace) and click Save. Then click History and you can see the exact changes that you made and even revert.
I've never used it though, not sure how useful it is.
There is also a Workspace feature in the Dev Tools options which might have something closer to what you are looking for.